Magnetic resonance imaging will be applied to the study of regional myocardial perfusion using both a perfused and in vivo rabbit heart model. For the proposed research, 19F nuclear magnetic resonance imaging and spectroscopy will be used in the measurement of regional myocardial blood perfusion and cardiac output. These studies utilize a water-soluble agent. In addition, a non-water soluble fluorinated agent (FC-43) will be investigated for its ability to delineate areas of vascular damage and its potential in reducing infarct size. Preliminary results indicate that perfluorocarbon emulsions have potential as imaging agents delineating for the "bed-at-risk" and indicators of the severity of ischemic injury following reperfusion. Based upon these initial exciting results, it is now possible to begin to analyze the protective effects of various drug treatments in view of micro- vascular and vascular damage and myocytic cell injury. Regional measurements of high energy phosphate stores will be made using NMR surface coil methods. These measurements will be made in association with 19F NMR imaging in order to explore the relationship between regional myocardial blood perfusion and intracellular pH and high energy phosphate levels. The NMR methods to be utilized in this study permit the noninvasive and essentially continuous measurement of regional metabolism and fluorocarbon distribution in the perfused and in vivo heart prior to and during occlusion, and following stenosis or infarct with reperfusion. The long term objectives of the proposed research include the determination of the potentials of fluorocarbons in (a) aiding in the clinical management of ischemic heart disease and (b) as agents for NMR imaging for assessment of infarct size, vascular patency, and myocardial perfusion.